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larsbrinkhoff / old-simh

Adding Arpanet, Imlac, and TT2500 to SIMH
http://bitsavers.trailing-edge.com/pdf/bbn/imp/BBN1822_Jan1976.pdf
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CH11 problem. #3

Closed larsbrinkhoff closed 5 years ago

larsbrinkhoff commented 6 years ago

Making notes so I can ask people for advice.

larsbrinkhoff commented 6 years ago

The problem seems to begin with an incoming UDP packet of size 514. Minus the CHUDP header that is 510 bytes, or 255 words. @bictorv, is this an OK packet for CHUDP? Is it correct that this is the maximum size for a Chaosnet packet (504 payload + 6 hardware header bytes)?

This is read in SIMH as a packet of size 497, so obviously that is a problem.


        0x0000:  4500 021e 0a6a 4000 4011 6934 ac1f 0164
        0x0010:  5863 bf4a a43a a43b 020a c74c 0101 0000
        0x0020:  8000 01e8 064e 0201 0668 0812 0002 0001
        0x0030:  538d 5445 4154 4c42 2d45 5250 504f 5245
        0x0040:  4954 5345 4420 4e4f 2d54 4552 5041 4e20
        0x0050:  544f 422d 4341 454b 2d44 5055 4120 5455
        0x0060:  4f48 2052 5243 4145 4954 4e4f 442d 5441
        0x0070:  2045 4552 4546 4552 434e 2d45 4144 4554
        0x0080:  428d 4f4c 4b43 532d 5a49 2045 3633 3638
        0x0090:  8d34 4850 5359 4349 4c41 562d 4c4f 4d55
        0x00a0:  2d45 5246 4545 422d 4f4c 4b43 2053 3a30
        0x00b0:  3231 3039 8d31 448d 4b53 203a 414c 5352
        0x00c0:  203b 4c2e 5349 2e50 4f20 5455 5550 8d54
        0x00d0:  4850 5359 4349 4c41 562d 4c4f 4d55 2045
        0x00e0:  8d30 4c42 434f 2d4b 4953 455a 3320 3836
        0x00f0:  3436 4c8d 4e45 5447 2d48 4e49 422d 4f4c
        0x0100:  4b43 2053 8d30 5942 4554 532d 5a49 2045
        0x0110:  3633 4c8d 4e45 5447 2d48 4e49 422d 5459
        0x0120:  5345 3020 438d 4552 5441 4f49 2d4e 4144
        0x0130:  4554 3020 2f39 3732 312f 2038 3830 303a
        0x0140:  3a39 3531 528d 4645 5245 4e45 4543 442d
        0x0150:  5441 2045 3031 302f 2f33 3831 3020 3a30
        0x0160:  3030 303a 8d30 5541 4854 524f 4c20 5241
        0x0170:  8d53 448d 4b53 203a 414c 5352 203b 5341
        0x0180:  3738 3834 3320 8d38 4850 5359 4349 4c41
        0x0190:  562d 4c4f 4d55 2045 8d30 4c42 434f 2d4b
        0x01a0:  4953 455a 3320 3836 3436 4c8d 4e45 5447
        0x01b0:  2d48 4e49 422d 4f4c 4b43 2053 8d34 5942
        0x01c0:  4554 532d 5a49 2045 3633 4c8d 4e45 5447
        0x01d0:  2d48 4e49 422d 5459 5345 3320 3930 8d30
        0x01e0:  5243 4145 4954 4e4f 442d 5441 2045 3930
        0x01f0:  302f 2f35 3831 3020 3a33 3035 343a 8d30
        0x0200:  4552 4546 4552 434e 2d45 4144 4554 3120
        0x0210:  2f30 3330 312f 2038 064e 0668 f25e
bictorv commented 6 years ago

A Chaos packet is indeed max 504 bytes (or 4032 bits if you read MIT AIM 628), and on some media (incl CHUDP, excl Ethernet) a "hardware trailer" of 6 bytes is appended. CHUDP pre-pends a 4-byte header. So 514 would be the max for a CHUDP pkt.

larsbrinkhoff commented 6 years ago

Thanks!

bictorv commented 5 years ago

A Chaos packet is indeed max 504 bytes (or 4032 bits if you read MIT AIM 628), and on some media (incl CHUDP, excl Ethernet) a "hardware trailer" of 6 bytes is appended. CHUDP pre-pends a 4-byte header. So 514 would be the max for a CHUDP pkt.

Plus 48 bits of header, so 510 bytes. Plus trailer and CHUDP header.

larsbrinkhoff commented 5 years ago

It seems to work fine with VAX and PDP-11 software. I haven't tested ITS.

We have a PDP-10 I/O bus CH10 in the works. It's a slightly modified CH11.

There were a Qbus version of CH11. Comments in MINITS say it worked a little bit differently from CH11, but as far as I can see the actual code is exactly the same.

bictorv commented 5 years ago

In other news, the chaosnet-bridge now supports Chaosnet-over-TLS, which is more reliable, works without a stable IP, and actually seems faster (ymmv, of course).